Coherence and Replacement Protocol of DICE - A Bus-Based COMA Multiprocessor

Sangyeun Cho, Jinseok Kong, Gyungho Lee

Research output: Contribution to journalArticlepeer-review

5 Citations (Scopus)


As microprocessors become faster and demand more bandwidth, the already limited scalability of a shared bus decreases even further. DICE, a shared-bus multiprocessor, utilizes cache only memory architecture (COMA) to effectively decrease the speed gap between modern high-performance microprocessors and the bus. DICE tries to optimize COMA for a shared-bus medium, in particular to reduce the detrimental effects of cache coherence and the "last memory block" problem on replacement. In this paper, we present the coherence and replacement protocol of the DICE multiprocessor and its design trade-offs. We describe a four-state write-invalidate coherence protocol in detail. Replacement, which poses a unique overhead problem of COMA, requires that a victim block with ownership be relocated to a remote node in order not to discard the last cached memory block. We show that the relocation process can be efficiently implemented by using a temporary storage called relocation buffer and a priority-based selection algorithm. We present performance results that show a drastic reduction in global bus traffic compared to a traditional shared-bus multiprocessor architecture.

Original languageEnglish
Pages (from-to)14-32
Number of pages19
JournalJournal of Parallel and Distributed Computing
Issue number1
Publication statusPublished - 1999 Apr

Bibliographical note

Funding Information:
We would like to thank the former members of the DICE project: Manu Agarwal, Sujat Jamil, Bland Quattlebaum, and Professor Larry Kinney in the Electrical and Computer Engineering Department, University of Minnesota. We also appreciate the constructive comments made by anonymous referees, which greatly helped improve the quality of this paper. The DICE project was supported by a funding from Samsung Electronics, Seoul, Korea and by a DoD AFOSR grant under Contract F49620-96-1-0472. Sangyeun Cho was supported in part by a fellowship from the Korea Foundation for Advanced Studies.


  • Distributed shared memory (DSM)
  • Shared bus
  • Symmetric multiprocessor (SMP)

ASJC Scopus subject areas

  • Software
  • Theoretical Computer Science
  • Hardware and Architecture
  • Computer Networks and Communications
  • Artificial Intelligence


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